/*
  * Mirante Tecnologia
  * Copyright 2010, Mirante Informatica LTDA, 
  * and individual contributors as indicated by the @authors tag
  *
  * This is free software; you can redistribute it and/or modify it
  * under the terms of the GNU Lesser General Public License as
  * published by the Free Software Foundation; either version 2.1 of
  * the License, or (at your option) any later version.
  *
  * This software is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this software; if not, write to the Free
  * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
  * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
  */
package com.miranteinfo.seam.hibernate;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.FlushMode;
import org.hibernate.HibernateException;
import org.hibernate.event.AutoFlushEvent;
import org.hibernate.event.AutoFlushEventListener;
import org.hibernate.event.EventSource;

import com.miranteinfo.seam.hibernate.envers.EnversConfiguration;

/**
 * Override hibernate auto flush event listener to support our persist logic.
 * 
 * @author lucas lins
 *
 */
public class HibernateAutoFlushEventListener extends HibernateFlushEventListener implements AutoFlushEventListener{
	
	private static final long serialVersionUID = 1L;

	private static final Log log = LogFactory.getLog(HibernateAutoFlushEventListener.class);
	
	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	// constructor
	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	
	public HibernateAutoFlushEventListener(EnversConfiguration envers){
		super(envers);
	}
	
	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	// on-flushing section
	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	
	/** Handle the given auto-flush event.
	 *
	 * @param event The auto-flush event to be handled.
	 * @throws HibernateException
	 */
	public void onAutoFlush(AutoFlushEvent event) throws HibernateException {

		final EventSource source = event.getSession();
		
		if ( flushMightBeNeeded(source) ) {

			final int oldSize = source.getActionQueue().numberOfCollectionRemovals();

			flushEverythingToExecutions(event);
			
			if ( flushIsReallyNeeded(event, source) ) {

				log.trace("Need to execute flush");

				performExecutions(source);
				postFlush(source);
				// note: performExecutions() clears all collectionXxxxtion 
				// collections (the collection actions) in the session

				if ( source.getFactory().getStatistics().isStatisticsEnabled() ) {
					source.getFactory().getStatisticsImplementor().flush();
				}
				
			}
			else {

				log.trace("Dont need to execute flush");
				source.getActionQueue().clearFromFlushNeededCheck( oldSize );
			}
			
			event.setFlushRequired( flushIsReallyNeeded( event, source ) );

		}

	}

	private boolean flushIsReallyNeeded(AutoFlushEvent event, final EventSource source) {
		return source.getActionQueue()
				.areTablesToBeUpdated( event.getQuerySpaces() ) || 
						source.getFlushMode()==FlushMode.ALWAYS;
	}

	private boolean flushMightBeNeeded(final EventSource source) {
		return !source.getFlushMode().lessThan(FlushMode.AUTO) && 
				source.getDontFlushFromFind() == 0 &&
				source.getPersistenceContext().hasNonReadOnlyEntities();
	}
	
}
